(i) Field of the Invention
The present invention relates generally to a rotary machine, and more specifically to a rotary type fluid machine.
(ii) Description of the Prior Art
The typical construction of a scroll-type compressor, for instance, generally known in art of the fluid compression machines as shown in FIG. 10, a schematic view showing the general principle of operation, is such that there are provided two scroll or spiral elements of an identical cross-sectional shape, one spiral element 2 being fixed in position onto the surface of a sealing end plate having a generally central delivery opening 4. Further to this construction, these two spiral elements are shifted in rotation relatively 180 degrees apart from each other and are also shifted in relative location by a distance 2 .rho.(=the pitch of a spiral pattern -2 X thickness of a spiral element plate) so as to be nested in position with each other in such a manner as schematically shown in the figure that they may be located in their relative position to come in abutting contact with each other at four points 51, 52 and 51', 52'. According to this construction, it is further noted that the one spiral element 2 is disposed stationary in position, and the other element 1 is arranged to move in revolution or in solar-orbital motion with a radius of .rho.=0, 0' about the center 0 of the spiral element 2, without moving in rotation or in planetary motion on its own axis, by using a crank mechanism having a radius .rho..
With such construction, there are defined small spaces or chambers 3, 3 being tightly enclosed extending along and between the abutting points 51, 52 and 51', 52' of the spiral elements 1, 2, respectively, the volumes of which chambers 3, 3 vary gradually in continuation with the solar or revolving motion of the spiral element 1.
Reviewing more specifically, it is notable that when the spiral element 1 is firstly caused to be revolved 90 degrees starting from the position shown in FIG. 10 (A), it turns now to be in the state as shown in FIG. 10 (B), when it is revolved 180 degrees, then it turns to be in the state as shown in FIG. 10 (C), and when it is further revolved 270 degrees, it turns then to be in the state as shown in FIG. 10 (D). As the spiral element 1 moves along in revolution, the volumes of the small chambers 3, 3 decrease gradually in continuation, and eventually, these chambers come in communication with each other and merge into one tightly enclosed small chamber 53. Now, when it moves in revolution further 90 degrees from the state shown in FIG. 10 (D), it turns back to the state in position as shown in FIG. 10 (A), and the small chamber 53 would then be caused to be reduced in its volume as it turns from the state shown in FIG. 10 (B) to that shown in FIG. 10 (C), and eventually it would turn to a smallest volume intermediate the states shown in FIGS. 10 (C) and (D). During this stage of motion in revolution, outer spaces starting to be opened as seen in FIG. 10 (B) get grown to be greater as the element 1 turns along from the state of FIG. 10 (C) through the state of FIG. 10 (D) to the state of FIG. 10 (A), thus introducing another volume of a fresh air from these outer spaces into the tightly enclosed small chamber to be eventually merged together, and then repeating this cycle of revolutionary motion so that the gas thus-taken into the outer spaces of the spiral elements may accordingly be compressed, thus being delivered out of the delivery opening 4.
The foregoing description is concerned with the general principle of operation of the scroll-type compressor, and now, referring more concretely to the construction of this scroll-type compressor by way of FIG. 11 showing in longitudinal cross-section the general construction of the compressor, it is seen that a housing 10 is comprised of a front end plate 11, a rear end plate 12 and a cylinder plate 13. The rear end plate 12 is provided with an intake port 14 and a delivery port 15 both extending outwardly therefrom, and further installed securely with a stationary scroll member 25 comprising a spiral or helical fin 252 and a web disc 251. The front end plate 11 is adapted to pivotally mount a spindle 17 having a crank pin 23. As typically shown in FIG. 12 which is a transversal cross-sectional view taken along the plane defined by the arrow XII--XII in FIG. 11, in mutually operative relationship with the crank pin 23 there is seen provided a revolving scroll member 24 including a spiral element 242 and a disc 241, through a revolving mechanism, which comprises a radial needle bearing 26, a boss 243 of the revolving scroll member 24, a square-section sleeve member 271, a slider element 291, a ring member 292 and a stopper lug 293 and the like.
The practice of design engineering of the general configuration of the scroll or spiral elements 1, 2 to be incorporated in the scroll-type compression machine is, as described in detail in the Japanese Patent Application No. 197,672/1981 filed by the present inventors, such that the major parts of the radially inner and outer profile curves of these spiral elements may generally be designed consisting of the involute functions. As stated also in the description on the principles of operation of this type compression machine given above, the small chamber 53 would change in reduction its working volume for a certain part of its operation cycle, thus providing the delivery of high pressure fluid out of the delivery port. In connection with this cycle of operation, there is encountered the phenomenon of so-called "top clearance volume" arising from the fact that the volume of the small chamber cannot be zeroed or excluded from existence because of a thickness of the spiral element which cannot be made nullified in the actual design of construction.
Reviewing more specifically, as shown further in detail in FIG. 13, an enlarged fragmentary view of the core portions of the spiral elements, in which drawing figure (A) corresponds to FIG. 10 (C), the small chamber 53 defined between the points of contact 52 and 52' of the two complementary spiral elements 1, 2 will be in its working position as shown in a similar manner in FIG. 13 (B), when the spiral element 1 is caused to be moved in revolutionary motion, where the volume of the small chamber 53 turns out to be smallest. Then when the spiral element 1 is moved further in revolution passing this specific point of engagement, the spiral elements 1, 2 are departed away from each other, thus having the points of contact therebetween 52, 52' dissolved accordingly. On this moment, the small chamber 53 as defined between these two spiral elements 1, 2 now turns in communication with the small chambers 3,3 defined outside of each of the spiral elements.
From this locational relationship in the generally known construction of the rotary machine, it is inevitable that the fluid under high pressure confined in the then smallest volume as shown in FIG. 13 (B) is therefore put again in communication with the small chambers 3, 3, instead of being delivered out of the delivery port 4. For this reason, the work done thus far upon the fluid body corresponding to the top clearance volume in question would immediately be turned out to be a loss of work, accordingly.
Also, as it is the general practice of design engineering in the conventional rotary machine construction that the leading ends of the spiral elements 1 and 2 are of a sharp corner, it would then be subjected to damages with a relatively high possibility during the operation. Moreover, this sharp-cornered leading end of the spiral element would generally require an additional number of man-hours in the machining work.
In coping with these drawbacks which are particular to the conventional rotary fluid machines as referred to above, the present inventors have previously proposed the provision of the rotary type fluid machine construction which is equipped with the spiral element of the type as specifically shown in FIG. 14, by way of the frontal elementary view, of the Japanese Patent Applications Nos. 206,088/1982.
Referring more specifically to the construction according to this Japanese Patent Application, the general construction is of such as shown schematically in FIG. 14 that there is provided the stationary spiral element designated at the reference numeral 501, wherein the curves of the radially outer and inner surfaces of the spiral element 501 are designated at 601 and 602, respectively. It is seen that the radially outer curve 601 is defined as an involute curve having the base circle radius b and the starting point A, the curve section E-F of the radially inner curve 602 is an involute curve having the shift in phase of (.pi.-.rho./b) with respect to the radially outer curve 601, and the curve section D-E is an arc having the radius R. Also, the connection curve designated at 603 for connecting smoothly the radially outer and inner curves 601 and 602 is an arc having the radius r. The point A is the starting point of the outer curve 601 in the involute curve, and the point B is the boundary point between the outer curve 601 and the connection curve 603, where the both curves share the same tangential line. The point C is the one that is defined sufficiently outside of the radially outer curve 601, and the point D is the boundary point between the inner curves 602 and the connection curve 603, at which point there are two arcs having the radii R and r in osculating relationship with each other. The point E is the boundary point between the arc section (between the points from D to E) of the radially inner curve 602 and the involute curve section E-F, where the both curves share the same tangential line. The point F is seen to be the one which exists sufficiently outside of the inner curve 602.
It is noted that the other revolving spiral element 502 is in the identical construction.
Now, the radii R and r may be given with the following equations; that is EQU R=.rho.+b.beta.+d (1) EQU r=b.beta.+d (2)
where,
.rho. is the radius of revolutionary motion; PA1 b is the radius of a base circle ##EQU1## .beta. is a parameter.
The parameter .beta. is equal to an angle defined by a straight line segment passing the origin 0 and the X-axis in the negative guadrant. Two points of intersection of the straight line segment passing the origin 0 and at the angle of .beta. and the base circle are seen existing in the line segments EO.sub.2 and BO.sub.1. It is also seen that the straight line segments EO.sub.1 and BO.sub.1 extend in osculation with the base circle at the points of intersection noted above.
More specifically, it is noted that the parameter .beta. is defined to be a given marginal condition for the establishment of the involute curve for the radially outer and inner curves in the configuration of the spiral element, and conversely that this parameter .beta. would eventually define the marginal points E and B for the attainment of a due involute curve.
According to the general construction of the rotary fluid machine, it is the practice of design engineering such that the curvilinear section extending between the points E and B may appropriately be determined for avoiding contacts of the both spiral elements therebetween, and that the marginal point for abutting contact between these two elements with the curve extending from the outerior point of contact would then turn to be the points E and B. According to this practice of engineering, it is generally accepted that while the point E on the part of the stationary spiral element would abut in contact with the point B of the revolving spiral element, the curved profile of these elements is designed in such a manner that they may depart from each other in their relative motion during the operation.
Now, referring to FIG. 15, there are shown a revolving spiral element at the reference numeral 502 having points of engagement or contact 552 and 552' between these spiral elements, a small space or chamber at 553 defined between the points of contact 552 and 552', and outer spaces or chamber 503, 503, respectively. It is noted that FIG. 15 (A) corresponds to FIG. 13 (A), and FIG. 15 (B) corresponds to FIG. 13 (B), respectively, and that FIGS. 15 (C), 15 (D) and 15 (E) show the positions taken by the spiral element 502, when revolved further in sequence, respectively.
According to the specific construction of this proposition, it is notable that when the both spiral elements 501 and 502 are put to be moved in revolving motion relatively with each other in sequence as seen in FIGS. 15 (A), 15 (B), 15 (C), 15 (D) and 15 (E), the space or volume of the small chamber 553 as defined between the points of contact 552, 552' would continue to decrease gradually till the moment that the points of contact 552 and 552' would eventually merge into one and the same point as shown in FIG. 15 (E), whereupon the current volume of the small chamber 553 would then be turned to be zero or nullified.
As reviewed from the above description, it is noted that because of the so-called top clearance volume being nullified accordingly, otherwise left existing in the conventional construction, the whole volume of fluid thus being put under pressure is then delivered forcedly out of the delivery port (not shown) without any loss at all. Therefore, the total work done upon the fluid by the compression machine would duly be effected, thus preventing any loss of work from occurring which was otherwise inevitable during the operation construction of the conventional rotary fluid machine accordingly.
While the working capacity of the delviery port is neglected in the practice stated above for the convenience of explanation, it is actually required to provide a delivery port at an appropriate position in which there is defined the small chamber 553. It is inevitable in practice that there is produced more or less the top clearance volume in this practice noted above, but this will end to a substantially small extent, so small that it may well be estimated as being substantially null after all.
It is also notable that each of the central leading ends of the spiral elements 501 and 502 is, as typically shown in FIG. 14, of no sharp corner by virtue of the adoption of the arcuate joint or connection curve 603. For this reason, there may well be avoided a risk of breakage or damage of this leading end portion in question from occurring during the operation of the machine, and in addition, it will substantially contribute to an ease of machining of the spiral element that there are provided the arcuate curves in connection between the points D and E of the radially inner curve 602 and in the connection curve 603 per se, respectively.
By virtue of the adoption of the above noted proposition, while many drawbacks may be dissolved accordingly, thus effecting many advantages, there would occasionally be unavoidable the following inconveniences; that is,
(I) More specifically, it is noted that there are three factors of design determining the general configuration of the spiral element, which are: the radius b of a base circle for an involute curve, a radius of revolutionary motion .rho. and an angular parameter .beta. (which represents a marginal condition on the definition of an involute curve). However, in the actual manufacture of the fluid machine, it is the general practice to use the end mill cutter, which would therefore bring a certain practical restriction on the diameter of a mill cutter to be used in the machining conditions. According to the construction as disclosed in the Japanese Patent Application No. 206,088/1982, there is found the case that the use of the end mill cutter of a small diameter should have been forced from the restriction on the curvature R of the arcuate section E-D in the profile of the spiral element. From such restrictions, there would be the case that an error in machining or a period of work of the spiral element be increased inevitably from a shortage of the rigidity of an end mill cutter, or the like.
(II) Further, there would possibly be rendered an abnormal force upon the both spiral elements, when there is a certain degree of error in machining work of the both spiral elements or when there is an error in the relative locational relationship between the both spiral elements.
In the case of a scroll-type compressor, for example, it is the general trend that the abnormal force noted above would possibly grow greater during the operation under a high load where there exists a large difference between the low pressure and high pressure levels in the operation of the machine. Under such a condition, there is a great possibility that the leading end near the arc having the radius r of the spiral element shown in FIG. 14 would then be damaged because of the relatively small rigidity in this leading end portion.
In the fluid machine wherein the both spiral elements are designed to be in contact with each other, since the relative rate of slipping in the radially inward curved surfaces of the both spiral elements would turn out to be much greater than that in the radially outer portions thereof, there would then occur a greater amount of wear or abrasion in the radially inner surface of the element. When the extent of such abrasion would occasionally grow higher than the allowable maximum limit during a high load operation of the machine, thus producing an excessive amount of dust from abrasion in the inside of the compressor or associated parts, which would eventually result in a failure of the machine.
Even in the case that the both spiral elements are designed to be of non-contact type, when there is a certain degree of error in machining work of the both spiral elements, or when there is an error in the relative locational relationship between the both spiral elements incorporated, there would also be a substantial extent of wear or abrasion in the leading end portions of the complementary elements engaged during the operation of the machine, thus possibly resulting in a failure or like disorder.
(III) In the construction of a compressor wherein there are incorporated therein the spiral elements 252, 242 having the configuration as noted hereinbefore, it has sometimes been experienced that when in a high load operation in which there exists generally a substantial difference in pressures as found between the low pressure side and the high pressure side of the machine, there is a case that the radially inner leading end portion of the elements would occasionally be broken during the operation, and this is because the rigidity or stiffness of this specific inner leading end portion of the spiral element as shown by an arrow in FIG. 10 (A) is relatively smaller than that at any other portions.
In addition, in the design of the fluid machine wherein the both spiral elements are installed in mutually contact relationship, there would possibly occur a greater amount of wear or abrasion in the radially inner surface of the element, since the relative rate of slipping in the radially inward curved surfaces of the both spiral elements would turn out to be much greater than that in the radially outer portions thereof. On the other hand, in the case of the fluid machine construction wherein the both spiral elements are designed to be not in contact with each other, when there is a certain error in machining work of the both spiral elements, or an error in the relative locational relationship therebetween when installed together, there would likely be a possibility of breakage or abnormal abrasion in the complementary elements involved, particularly in the leading end portions thereof during the operation of the machine.